Spatial light modulators (SLMs) are devices or arrays of one or more devices that can control or modulate an incident beam of light in a spatial pattern that corresponds to an electrical input to the devices. The incident light beam can be modulated in intensity, phase, polarization or direction. Some modulation can be accomplished through the use of micro electromechanical systems (MEMS) in which electrical signals move micromechanical structures to modulate light incident thereon.
One type of MEMs based SLM is a ribbon light modulator, such as a Grating Light Valve (GLV™) commercially available from Silicon Light Machines, Inc., of Sunnyvale, Calif. Referring to FIG. 1, a ribbon light modulator generally includes a number of ribbons 102 each having a light reflective surface supported over a reflective surface of a substrate 104. One or more of the ribbons are deflectable toward the substrate to form an addressable diffraction grating with adjustable diffraction strength. The ribbons 102 may be electrostatically deflected towards the substrate 104 by integrated drive electronics formed in or on the surface of the substrate. Light reflected from the movable ribbons adds as vectors of magnitude and phase with that reflected from stationary ribbons or a reflective surface beneath the ribbons, thereby modulating light reflected from the SLM.